F.9.6.6 The round functions

1

• round((+-)0) returns (+-)0.

• round((+-)(inf)) returns (+-)(inf).

2

The double version of round behaves as though implemented by

#include <math.h>
#include <fenv.h>
#pragma STDC FENV_ACCESS ON
double round(double x)
{
     double result;
     fenv_t save_env;
     feholdexcept(&save_env);
     result = rint(x);
     if (fetestexcept(FE_INEXACT)) {
          fesetround(FE_TOWARDZERO);
          result = rint(copysign(0.5 + fabs(x), x));
     }
     feupdateenv(&save_env);
     return result;
}

The round functions may, but are not required to, raise the “inexact” floating-point exception for non-integer numeric arguments, as this implementation does.